The show, airing at 11:30 p.m. EST on NBC, has plenty of potential, with these two master entertainers headlining its comedy and merriment.

Short will be back at a former workplace. Now 62, he was an “SNL” regular during the 1984-85 season, before returning as guest host in 1986 and 1996, then making cameo appearances in 2005 and 2006.

It’s the fourth appearance as musical guest for McCartney, 70.

How did “SNL” happen to book this pair of for-all-ages favorites?

“The Christmas show has to have an emotional component,” explained “SNL” executive producer Lorne Michaels. “Besides, we have a long break following that show, when people are going to have lots of time to talk about it. So it’s always better to leave on a high note.”

Short’s resume includes films, stage performances and concerts, but many viewers remember him fondly from TV, and particularly from the landmark sketch show, “SCTV,” in the early 1980s. It was there that he introduced such characters as doddering tunesmith Irving Cohen and odd man-child Ed Grimley.

Some 30 years later, “Marty remains totally contemporary,” Michaels said Monday. “And the (‘SNL’) cast just adores him. He’s one of those people that a younger generation who does this kind of work connects with — and has held onto fast.”

Interviewed last week, Short said he didn’t anticipate butterflies when returning to his old haunts.

“I continually work in front of audiences, doing concerts here and there, so it keeps me loose,” he said. “You realize that the audience isn’t so interested in every joke being perfect. What they want, after the show, is to be able to say, `I felt like I had a hang with him. He seemed in the moment. He looked like he was having fun.’

“When I’m in front of an audience, I’m very loose,” Short said. “I get pumped, but I don’t get scared like I did years ago.”

Besides, he expected that returning to Studio 8H at Rockefeller Center in New York City would prove to feel comfortably familiar.

“Once you’ve done `Saturday Night Live,’ it becomes part of your extended life and you remember it forever,” he said. “I have such specific memories from when I was a regular! Like looking out the window at the Christmas tree and skaters.”

Short can expect to feast his eyes on the tree and skaters this week, too. Meanwhile, among the “SNL” cast members he will be joining is Jason Sudeikis, whose future with the show has been a topic of conjecture. With the defeat in November of presidential hopeful Mitt Romney (one of Sudeikis’ signature impersonations), there was talk the seven-season veteran might opt to depart “SNL” as soon as the Christmas break.

Not so, said Michaels.“I’m not sure Jason knew when he signed it, but he did sign a lifetime contract,” Michaels joked. “Of course, he has good lawyers and they’re examining it. But my sense is, we’ll have him for the rest of the season, and I’d like to keep him for longer than that.